In recent years, a pixel size has been reduced for imaging units (solid-state imaging units) such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor. As a result, the number of photons that enter a unit pixel (an imaging device) has decreased, and an S/N ratio has been reduced, thereby causing a reduction in sensitivity and the reduction in S/N ratio. In addition, in a case where a color filter configured by two-dimensionally arranging red, green, and blue primary color filters is used for coloring, in a red pixel, which results in a reduction in sensitivity. Moreover, in a case where each color signal is generated, interpolation processing is performed between pixels and thus a so-called false color is produced.
For example, PTL 1 discloses an imaging device in which an organic photoelectric conversion film including one layer is formed, a signal of one color is extracted by this organic photoelectric conversion film, and signals of two colors are extracted by silicon (Si) bulk spectroscopy. In such an imaging device, as electric field intensity to be applied to the photoelectric conversion film is higher, external quantum efficiency (EQE) in the photoelectric conversion film during application of light is larger. However, in a case where a large external voltage is applied, an electron or a hole is injected into the photoelectric conversion film from a pair of electrodes with the photoelectric conversion film interposed therebetween. This causes an increase in dark current and a decrease in S/N ratio.
In contrast, for example, PTL 2 discloses a solid-state imaging device that prevents generation of a dark current by providing an electron blocking layer and a hole blocking layer between a photoelectric conversion layer and a pair of electrodes.